1. Field of the Invention
The present invention relates to the field of image displaying techniques, and in particular to a panel display and manufacturing method thereof, panel display device.
2. The Related Arts
Optical etching process is important to the manufacturing of panel display device. The main steps comprise: thin film deposition→photo-resist coating→exposure→photo-resist lithography→thin film etching→photo-resist removal. Under normal circumstances, photo-resist lithography uses liquid lithography solution, and the thin film etching of metal (alloy) layer uses liquid etching solution for etching. Both are so called wet processes. In wet process, the thin film pattern on substrate will affect the partial density of the ingredient in the solution. That is, if the area of the photo-resist or the area of the metal (alloy) requires lithography is large, more ingredient will be consumed; on the other hand, if the area of the photo-resist or the area of the metal (alloy) requires lithography is small, less ingredient will be consumed.
Solution has a diffusion effect to maintain the same density everywhere in the solution. When differences exist in the thin film patterns on the substrate, the ingredient in the solution will diffuse from high density place to lower density place during the lithography or etching process, which leads to different lithography or etching result for boundary area of the pattern and the center area of the pattern. This effect is referred to as loading effect.
The following takes photo-resist lithography process of pixel electrode layer of liquid crystal panel as example to explain the bad influence of loading effect on active area (AA) of liquid crystal panel.
FIG. 1 shows a design of pixel electrode layer of a known liquid crystal panel. The center of the panel is active area 1, which has small photo-resist area requiring lithography. The majority outside of active area 1 is vacant area 2, which has large photo-resist area requiring lithography. By enlarging the view of the boundary area A′ of active area 1 in FIG. 1, the inner side design is normal pixel area 3, with tidy ITO electrode array, and the outer side design is vacant area (without ITO electrode array) 4. Because of loading effect, the actual photo-resist lithography process is different from the idealistic design. The actual result is shown in FIG. 2. Similarly, By enlarging the view of the boundary area A′ of active area 1 in FIG. 2, boundary area 5 near vacant area 4 will show pattern irregularity because of insufficient photo-resist lithography. The pixel irregularity becomes less towards the inner side, and the idealistic design appears at pixel area 3 that is in sufficiently inner side. The specific process of loading effect on photo-resist lithography is as follows: at the beginning of the lithography process, active area 1 slowly consumes a small amount of lithography ingredient and vacant area 2 rapidly consumes a large amount of lithography ingredient. The density different leads to lithography ingredient in active area 1 diffusing towards vacant area 2. From the perspective of boundary area A′ of active area 1, lithography solution density at boundary area 5 shows obvious gradient decreasing; that is, the closer to vacant area, the lower the density of lithography solution. In subsequent lithography process, lithography capability in boundary area 5 decreases in gradient manner, and the photo-resist lithography result is less for pixels closer to vacant area 4. Loading effect lessens the photo-resist lithography result of boundary area 5, which leads to pattern irregularity of etching process (mainly, unable to etch pattern or coarse etched pattern).
The pattern irregularity in boundary area 5 will cause defective image display. Not only the luminance, view angle and response time are different from those of normal pixel area 3, but also influences the charging and discharging characteristics of normal pixel area 3. Hence, it is desirable to eliminate pattern irregularity.